Sastav hrane i intenzitet ishrane lumbraka, Symphodus (Crenilabrus) tinca (Labridae), na južnim oblama Tunisa

The feeding habits of the peacock wrasse, Symphodus (Crenilabrus) tinca (Linnaeus, 1758), from the southern coast of Tunisia were investigated with respect to fish size and season. Stomach contents of 1334 specimens, 8.1-23.1 cm total length, were analyzed. Of the total, 1166 were empty (87.4%). This percentage varied over the year, with a maximum during the spawning period (May- July) and minimum in February and August. Crustaceans and mollusks constituted the main prey in both the small and large size classes. As fish grew, the proportion of isopods in the stomachs decreased and the proportion of shrimps and benthic organisms increased. Diet composition varied seasonally, with crustaceans the most important prey item in all seasons especially summer and autumn. Higher feeding activity in winter may be related to the reproductive cycle of the wrasse and the abundance of benthic organisms. Results indicate that the peacock wrasse feeds on a wide range of prey items and is an opportunistic predator.Istraživan je sastav hrane i intenzitet ishrane lumraka, Symphodus (Crenilabrus) tinca (Linnaeus, 1758) sakupljenog na južnim obalama Tunisa. Analiziran je sadržaj želuca kod 1334 primjerka ukupne veličine 8.1-23.1 centimetara, od kojih je 1166 (87.4%) primjeraka imalo prazan želudac. Intenzitet ishrane kolebao je tijekom godine od maksimuma za vrijeme sezone mriješćenja (svibanj-srpanj) do minimuma u veljači i kolovozu. U hrani su prevladavali rakovi i mekušci svih veličina. Shodno veličini ustanovljeno je da je kod većih primjeraka zastupljenost izopoda u ishrani manja, dok su rakovi i bentički organizmi više zastupljeni. Intenzitet ishrane kolebao je prema godišnjem dobu, iako su rakovi bili najvažniji plijen tijekom cijele godine, a posebno u ljeto i jesen. Viši intenzitet hranjenja u zimskom razdoblju može se pripisati periodu mrijesta lumbraka i povećanoj prisutnosti bentičkih organizama. Rezultati ukazuju da se lumbrak hrani širokim rasponom plijena, te je oportunistički predator

Starost i rast glavoča travaša Zosterisessor ophiocephalus Pallas, 1811 u zaljevu Gabes (Tunis, središnji Mediteran)

Zosterisessor ophiocephalus is currently an important component of the eastern Mediterranean inshore fisheries. In Tunisia it was recorded for the first time in the Gulf of Gabes in 1993, where it is now an important fished species. In this study age and growth parameters were determined in the Gulf of Gabes (southeast of Tunisia) based on otolith analysis of 824 specimens caught between September 2006 and August 2007. Monthly changes in marginal increments, determined from alternation of macroscopic opaque and translucent bands, of Zosterisessor ophiocephalus sagittae were examined. These results allowed us the estimation of the approximate age to the appearance of each annulus. The observed age was 6 years old for both sexes. Von Bertalanffy parameters based on length at age data were TL∞ = 24.83 ± 1.69 cm, K = 0.19 ± 0.03 year-1 and t0 = - 0.91 ± 0.12 for males and TL∞ = 24.13 ± 1.17 cm, K = 0.20 ± 0.02 year-1 and t0 = - 0.80 ± 0.09 for females. The length-weight relationship for both sexes of Zosterisessor ophiocephalus is Wt = 0.021 TL 2.789. The size at which 50% of females and males matured was respectively 12.65 cm and 13.91 cm total length (TL). The age at which 50% of females and males matured was respectively 2.9 and 3.5 years.Zosterisessor ophiocephalus je trenutno važna komponenta priobalnog ribolova istočnog Mediterana. U Tunisu je prvi put zabilježen u zaljevu Gabes 1993. godine, gdje je sada važna ribolovna vrsta. U ovoj studiji određivani su parametri starosti i rasta u zaljevu Gabes (jugoistočno od Tunisa) na temelju analize otolita 824 primjerka, ulovljenih između rujna 2006. i kolovoza 2007. godine. Starost je utvrđena na temelju fosilnih naraštajnih prstenova na otolitima (sagitta) vrste Zosterisessor ophiocephalus. Ovi rezultati su nam omogućili procjenu približne starosti pojavom svakog prstena kruga /annulus. Utvrđene su najstarije jednike koje su imale 6 godina za oba spola. Von Bertalenffyjevi parametri zasnovani na podatcima o duljini pri određenoj starosti bili su; TL∞ = 24.83 ± 1.69 cm, K = 0.19 ± 0.03 godina-1 i t0 = - 0.91 ± 0.12 za mužjake i TL∞ = 24.13 ± 1.17 cm, K = 0.20 ± 0.02 godina-1 i t0 = - 0.80 ± 0.09 za ženke. Dužinsko-maseni odnos za oba spola vrste Zosterisessor ophiocephalus je Wt = 0,021 TL 2.789. Veličina kod koje 50% ženki i mužjaka sazrijeva bila je 12,65 cm i 13,91 cm ukupne duljine (TL). Dob kod koje 50% ženki i mužjaka sazrijeva je između 2,9 i 3,5 godina starosti